1. Field of the Invention.
The present invention relates generally to utilizing drilling fluid in well cementing operations, and more particularly, to methods of cementing a well with a cementing composition which includes, as a component thereof, a portion of the drilling fluid used to drill the well.
2. Description of the Prior Art.
A variety of drilling fluids are used in drilling wellbores. Generally, the drilling fluids are solids-containing water based gels or hydrocarbon based fluids which can be non-weighted or weighted with particulate weighting material such as barite. After a wellbore is drilled, during which the drilling fluid used is circulated through the wellbore, the circulation of the drilling fluid is stopped while the well is logged and a string of pipe is run in the wellbore. After the pipe is run, the drilling fluid in the wellbore is cleaned up by circulating drilling fluid downwardly through the interior of the pipe and upwardly through the annulus between the exterior of the pipe and the walls of the wellbore while removing drilling solids and gas therefrom. Primary cementing operations are then performed in the wellbore, i.e., the string of pipe disposed in the wellbore is cemented therein by placing a cementing composition in the annulus between the pipe and the walls of the wellbore. The cementing composition sets into a hard substantially impermeable mass whereby the pipe is bonded to the walls of the wellbore and the annulus is sealed. When the cementing composition is run down the pipe and into the annulus, the drilling fluid in the pipe and annulus is displaced therefrom. The displaced drilling fluid which has been viewed as a waste material is generally accumulated in a pit or tank and then discarded.
Drilling fluid often must be treated as a fluid which is hazardous to the environment, therefor the disposal of drilling fluid, particularly from offshore drilling locations, is time consuming and expensive. Thus, any environmentally acceptable use to which all, or part, of the drilling fluid could be employed at a well site, to thereby eliminate the need for disposing of the drilling fluid, would be highly advantageous.
By the present invention, methods of cementing wells with cementing compositions containing drilling fluid are provided. That is, a portion of the drilling fluid used to drill a well is utilized as a component in the cementing composition used for cementing the well. The portion of the drilling fluid which is not utilized in the cementing composition can be disposed of conventionally, or it can be formed, by the method of this invention, into a hard mass for appropriate storage.